Any given field in agricultural lands is typically comprised of several different soil types, each of which may be categorized according to the relative proportions of sand, clay and silt it contains. While there are twelve generally accepted soil categorized or types, these categories generally fall into three broader categories, i.e. sandy, clay or loam. Sandy soils have the least capacity to hold water and nutrients and thus require the most fertilization, while clay soils have the greatest capacity to hold water and nutrients and thus require the least fertilization. Loam soils consist of a combination of sand, clay and silt and have fertilization requirements between those of sandy and clay soils. Although any given field may not include all three of the above described soil types, it would be most unusual if it did not include at least two substantially different soils having substantially different fertilization requirements.
Most fields contain one dominant soil type which covers the majority of the field area with the remaining area made up of other different soil types distributed around the field in various relatively smaller areas having curvilinear boundaries which often, but not necessarily, correspond to low or high spots. Ideally, each of the individual areas of different soil should be treated independently for the purpose of fertilization. However, heretofore there has not been any efficient, practical and economical fertilizing method or equipment for this purpose. Thus, the almost universal practice is to fertilize the entire field according to the needs of the most deficient soil, or according to the averaged requirements of the different soils. The result is that a substantial area of the field receives more and in the latter case less fertilizer than it requires, resulting in significant waste of expensive fertilizer and potentially lowering yields in less than optimally fertilized areas.
Thus, there has long been a need for an economical method and apparatus for applying fertilizer according to the needs of each different area of different soil type in a field. As will be demonstrated below, the present invention provides such method and apparatus.